What is this brown algea on sanbed

[merereef]

Tank is 3 months old and a gave the sand a good stirring a few nights ago and then noticed this brown algea.. dont know if its diatoms or dino when lights are on the brown slgea is a lot darker

The pics below are 3 hours after lights have gone out

 

[BadFish619]

Diatoms, normal for a new tank. Will go away on its own.

 

[merereef]

Diatoms, normal for a new tank. Will go away on its own.

I went through the diatoms stage about 3 months ago is it normal for it to happen again plus this time it seems darker? Thanks for the reply